page cache: Convert filemap_range_has_page to XArray

Instead of calling find_get_pages_range() and putting any reference,
use xas_find() to iterate over any entries in the range, skipping the
shadow/swap entries.

Signed-off-by: Matthew Wilcox <willy@infradead.org>

diff --git a/mm/filemap.c b/mm/filemap.c
index bedd8680f78949505651e2f44a024605d0a49d0c..6b36516bc31d85bb79db543e354734306381854e 100644 (file)
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -455,20 +455,31 @@ EXPORT_SYMBOL(filemap_flush);
 bool filemap_range_has_page(struct address_space *mapping,
                           loff_t start_byte, loff_t end_byte)
 {
-       pgoff_t index = start_byte >> PAGE_SHIFT;
-       pgoff_t end = end_byte >> PAGE_SHIFT;
        struct page *page;
+       XA_STATE(xas, &mapping->i_pages, start_byte >> PAGE_SHIFT);
+       pgoff_t max = end_byte >> PAGE_SHIFT;
 
        if (end_byte < start_byte)
                return false;
 
-       if (mapping->nrpages == 0)
-               return false;
+       rcu_read_lock();
+       for (;;) {
+               page = xas_find(&xas, max);
+               if (xas_retry(&xas, page))
+                       continue;
+               /* Shadow entries don't count */
+               if (xa_is_value(page))
+                       continue;
+               /*
+                * We don't need to try to pin this page; we're about to
+                * release the RCU lock anyway.  It is enough to know that
+                * there was a page here recently.
+                */
+               break;
+       }
+       rcu_read_unlock();
 
-       if (!find_get_pages_range(mapping, &index, end, 1, &page))
-               return false;
-       put_page(page);
-       return true;
+       return page != NULL;
 }
 EXPORT_SYMBOL(filemap_range_has_page);